Williams Welsh
Member
If Outlook has been running slow, freezing randomly, or throwing sync errors, there's a good chance your OST file has grown way beyond a healthy size. This is more common than people realize — OST files balloon quietly over time as emails, attachments, and calendar data pile up, and most users don't notice until things start breaking. The first thing to try is cleaning house inside Outlook itself: empty your Deleted Items and Junk folders, archive older emails you rarely access, and use the built-in Compact Now option under Account Settings to physically shrink the file on disk. If Outlook is connected to an Exchange server, check whether your mailbox quota has been exceeded, since that alone can trigger sync failures that make the OST grow unpredictably. For a thorough breakdown of why this happens and how to tackle it from every angle, this guide on the Outlook oversized OST file problem is worth reading through carefully. When the file is too far gone — corrupted, inaccessible, or simply unmanageable — converting it to PST is the cleanest fix. The Macsonik OST to PST Converter does this reliably on Mac, recovering your data intact without needing a live Exchange connection.